Oil refining system



May 16, 1939. w T. HANCOCK OIL REFINING SYSTEM Filed March 4, 1938 W RSv9 .SQ Mbw .ShwwkMl W. wnknm Mmmm mw n mw kmmb 9 bm f 1| v um. I tmuxw Nn mw v M Nm. QN f .nh QM. Nv?. lm i Ww Y \\J kmhb um n lllllllllll WN L--.fwn w w m.\\, ll'lllll'llll m v R, K

MN Sv @v JQM. W\ 3S@ Patented May 16, 1939 UNITED STATES PATENT OFFICEApplication March 4,

9 Claims.

This invention relates generally to the rening of petroleum oils, andhas to do particularly with an improvement in systems wherein an oil,preierably a suitable cracking stock, initially is pre- VVheated b-elowthe cracking temperature, and then is subjected to cracking followed byfractionation.

In the present type of reining system the charging stock is firstpreheated and then forced -by pump through a cracking still, the crackedoil ultimately being treated or fractionated in any suitable manner.Ordinarily the pump forcing the preheated oil through the cracking stilloperates at an inlet pressure corresponding to -the preheater outletpressure, which pressure may be subject to considerable variation,because of changing operating conditions, with relation to the crackingstill outlet pressure. Consequently the load on the pump discharging tothe cracking still is subject to variation in accordance with thechanging diierential between the pump inlet and outlet pressures. It isdesirable, for obvious reasons, that the pressure and throughput rateunder which the cracking still is operated be stable and uninfluenced byvariations in the relative outlet pressures and throughput of thepreheating and cracking stills, and accordingly it is the principalobject of this invention to insure that desirable stability in this typeof refining system.

In accordance with the invention, I provide what may be termed apressure balance column, having one section or chamber through which thepreheated charging stock flows to the cracking still feed pump, andanother chamber through which the cracked oil stream is discharged bythe pump from the cracking still to the fractionating equipment. Undertypical operating conditions the oil is cracked under substantialpressure, for example in the neighborhood of 150 lbs. per sq. in.Although the preheated oil and cracked oil ow through the pressurebalance column in separate streams, the chambers within the column arein communication so that the preheated oil is taken by the pump underpressure corresponding substantially to the vcracking still outletpressure. By thus avoiding possible substantial variations in thepressure differential under which the pump is required to operate, it ismade possible to greatly stabilize the operation of the system as awhole. To this same end, the pressure balance may be adapted to serve afurther purpose in providing a surge chamber -to compensate fortemporary excess in the rate of oil discharged from the preheating stillover 1938, Serial No. 193,935

the rate at which the oil has been put through the cracking still. Aswill appear, the pressure balance column may serve still furtherpurposes, such as to effect a substantial degree of heat exchangebetween the cracked oil and preheated oil streams, to release preheatedoil vapors into the cracked vapor stream, and to accomplish anintermediate fractionation of the cracked oil ahead of the nalfractionating stages.

The various objects and operation of the invention will perhaps mostreadily be understood and explained to best advantage by reference tothe accompanying drawing in now sheet form, showing a typical refiningsystem embodying the invention in one of its illustrative and preferredforms. It will be understood however that various changes andmodifications may be made, particularly in the structural form anddetails of the pressure balance column, without departure from theintended spirit and scope of the invention.

A suitable charging stock, for example gas oil, is supplied through lineI0 to the pump I I which forces the oil through the preheating coil I2.For purposes of illustration, coil I2 is shown in a preheating still I3separate fromthe cracking still I4, although it will be understood thatif desired, the preheating and cracking coils may be incorporated in asingle still structure. The oil is preheated in the still I3 to asuitable temperature, for example around 600 F., and is dischargedthrough line I5 to an apparatus generally indicated at I6, to which Ihave referred as the pressure balance column. The latter, in the typicalform shown, comprises a shell II containing upper and lowercommunicating chambers I8 and I9 separated by wall 20. Upper chamber I8preferably serves as a dephlegmating or fractionating zone, beingvertically elongated and provided with perforated plates 2| or othersuitable means for securing intimate contact between the rising crackedvapors and down owing reuX, as will later appear. Chamber I9 constitutesa lower zone through which the preheated oil flows from line I5 to theoutlet 22, thence to be forced under pressure by pump 23 through line 24of the cracking coil 25.

The cracked oil stream, heated to a temperature between 900 F. to 1100F. for example, preferably is discharged through line 26 into a suitablereaction chamber 21 preliminary to the delivery of the cracked vaporsthrough line 28 intovchamber I8. Carbon and unvaporized residuumseparated from the cracked oil stream in reaction chamberll, are removedfrom the reux condensate suitable for recirculation to system by way ofline 29, so that only uncontaminated and vaporized hydrocarbons passfrom the reaction chamber into the dephlegmating chamber I8. The crackedvapors are subjected to reflux condensation in owing upwardly throughthe perforated plates in chamber I8. The reflux condensate is withdrawnfrom the base of the chamber through outlet 38, and the vapors arewithdrawn through line 3| to be subjected to further fractionation. Aportion or all of the reflux condensate removed from chamber I8 may berecirculated for further cracking in coil 25, by way of the valvecontrolled line 32 connecting with the preheated oil line 22.

The cracked oil vapors leaving column I6 may be subjected to finalfractionation in any suitable manner, for example by introducing thevapors at 33 to the base of fractionating column 34 wherein fractionsheavier than gasoline are condensed and removed through line 35. Aportion of the condensate may be taken through line 36 and supplied byway of line 31 to the upper part of chamberv I8 to reflux thecracked oilvapors introduced thereto. The system may be operated to produce in thefractionating column 34 the cracking still, in' which event, all or aportion of the condensate may be discharged through lines 36 and 38 tobe combined with the preheated oil flowing through line 24 to thecracking still. Vapors leaving the fractionating column are passedthrough line 40 to final condenser 4I and thence to receiver 42 fromwhich the distillate is removed through line 43 and lixed gases throughline 44.. A substantial pressure, for example of about 150 lbs. per sq.in., or above, is maintained on the oil undergoing cracking, by asuitable pressure regulating valve placed beyond the pressure balancecolumn, for example at 45 between vthe pressure balance column and thefractionating column, or at 46 beyond the fractionating column.

A pressure balance between the preheated oil stream flowing from coil I2to the cracking coil 25, and the cracked oil stream at the high pressureside of the pressure regulating valve, is

maintained by providing pressure communication between chambers I8 andI9. Typically, the pressure connection between the chambers maycomprisea pipe 41 extendingY upwardly from the chamber partition 20within chamber I8 to a point above the uppermost of the perforatedplates 2`I. In addition to maintaining the pressure balance betweenchambers I8 and I9, pipe 41 also provides a passage through which anylight vapors Within chamber I9 are released into the cracked oil vapors,to be removed with the latter for fractionation in column 34. It will beobserved that by placing chambers I8 and I9 in pressure balance, thepressures at opposite sides of the pump 23 are in balance eX- cept forthe differential corresponding substantially to the pressure dropthrough the cracking still I4. As a result, the load on the pump isreduced to the point of low power requirement, and the constancy andeiciency of the pump operation are such as to eifectively stabilize theoperation of the entire system.v

Thus column I6 serves the several functions of v.maintainingsubstantially a pressure balance between the preheated and cracked oilstreams cracked vapor stream light oil fractions vaporized in thepreheating stage. Other features incident to the operation of thecolumn, are the maintenance of some heat transfer between the preheatedoil stream and the cracked reflux condensate, and also the capacity ofchamber I9 to serve as a surge chamber and thereby to compensate for anyvariations in the rates of oil discharge to the preheating and crackingcoils by pumps II and 23.

I claim:

l. In a petroleum refining system in which oil is passed undersubstantial pressure through a preheater and then through a crackingstill, a column comprising a vertically extending shell, a wall dividingthe interior of said shell into upper and lower chambers and preventingliquid from flowing from the upper chamber into the lower chamber, meansfor passing preheated oil from said preheater through one of saidchambers, a pump for then discharging the preheated oil to said crackingstill, means for passing cracked oil vapors from the cracking stillthrough the other of said chambers separately from the preheated oilflowing through the column, and means providing a pressure balanceconnection between the chambers to maintain the preheated and crackedoil leaving'said preheater and cracking still under substantially thesame pressure, whereby the pressure at the inlet side of said pump ismade to correspond substantially to the pressure of the oil leaving thecracking still.

2. In a petroleum refining system in which oil is passed undersubstantial pressure through a preheater and then through a crackingstill, a column comprising a vertically extending shell, a wall dividingthe interior of said shell into upper and lower chambers and preventingliquid from flowing from the upper chamber into the lower chamber, meansfor passing preheated oil from said preheater through one of saidchambers, a pump for then discharging the preheated oil to said crackingstill, means for passing cracked oil vapors from the cracking stillthrough the other of said chambers separately from the preheated oililowing through the column, means subjecting the cracked oil vapors toreiiux condensation within the last mentioned chamber, and meansproviding a pressure balance connection between the chambers to maintainthe preheated and cracked oil leaving said preheater and cracking stillunder substantially the same pressure, whereby the pressure at the inletside of said pump is made to correspond substantially to the pressure ofthe oil leaving the cracking still.

3. In a petroleum refining system in which oil is passed undersubstantial pressure through a preheater and then through a crackingstill, a column comprising a vertically extending shell, a wall dividingthe interior of said shell into upper and lower chambers and preventingliquid from flowing from the upper chamber into the lower chamber, meansfor passing preheated oil from said preheater through one of saidchambers, a pump for then discharging the preheated oil to said crackingstill, means for passing cracked oil vapors from the cracking stillthrough a reaction chamber wherein unvaporized residue is removed, andthen through the other of said chambers separately from the preheatedoil flowing through the column, and means providing a pressure balanceconnection between the chambers to maintain the preheated and crackedoil leaving said preheater and cracking still under substantially thesame pressure, whereby the pressure at the inlet side of said pump ismade to correspond substantially to the pressure of the oil leaving thecracking still.

4. In a petroleum rening system in which oil is passed under substantialpressure through a preheater and then through a cracking still, a columncomprising a vertically extending shell, a wall dividing the interior ofsaid shell into upper and lower chambers and preventing liquid fromflowing from the upper chamber into the lower chamber, means for passingpreheated oil from said preheater through one of said chambers, a pumpfor then discharging the preheated oil to said cracking still, means forpassing cracked oil vapors from the cracking still through a reactionchamber wherein unvaporized residue is removed, and then through theother of said chambers separately from the preheated oil flowing throughthe column, means subjecting the cracked oil vapors to refluxcondensation within the last mentioned chamber, and means providing apressure balance connection between the chambers to maintain thepreheated and cracked oil leaving said preheater and cracking stillunder substantially the same pressure, whereby the pressure at the inletside of said pump is made to correspond substantially to the pressure ofthe oil leaving the cracking still.

5. In a petroleum rening system in which oil is passed under substantialpressure through a preheater and then through a cracking still, a columncomprising a vertically extending shell, a wall dividing the interior ofsaid shell into upper and lower chambers and preventing liquid fromflowing from the upper chamber into the lower chamber, means for passingpreheated oil from said preheater through the lower chamber, a pump forthen discharging the preheated oil to said cracking still, means forpassing cracked oil vapors from the cracking still through the upperchamber separately from the preheated oil flowing through the column,and means providing a pressure balance connection between the chambersto maintain the preheated and cracked oil leaving said preheater andcracking still under substantially the same pressure, whereby thepressure at the inlet side of said pump is made to correspondsubstantially to the pressure of the oil leaving the cracking still.

6. In a petroleum rening system in which oil is passed under substantialpressure through a preheater and then through a cracking still, a columncomprising a vertically extending shell, a wall dividing the interior ofsaid shell into up'- per and lower chambers and preventing liquid fromflowing from the upper chamber into the lower chamber, means for passingpreheated oil from said preheater through the lower chamber, a pump forthen discharging the preheated oil to said cracking still, means forpassing cracked oil vapors from the cracking still through a reactionchamber wherein unvaporized residue is removed, and then through theupper chamber separately from the preheated oil ilowing through thecolumn, means subjecting the cracked oil vapors to reflux condensationwithin the last mentioned chamber, and means providing a pressurebalance connection between the chambers to maintain the preheated andcracked oil leaving said preheater and cracking still undersubstantially the same pressure, whereby the pressure at the inlet sideof said pump is made to correspond substantially to the pressure of theoil leaving the cracking still.

7. In apetroleum rening system in which oil is passed under substantialpressure through a preheater and then through a cracking still, a columncomprising a vertically extending shell, a wall dividing the interior ofsaid shell into a lower chamber and an upper chamber and preventingliquid from flowing from the upper chamber into the lower chamber, meansfor passing. preheated oil from said preheater through said lowerchamber, a pump for then discharging the preheated oil to said crackingstill, said lower chamber having sufcient volume to permit the preheatedoil to surge therein, means for passing cracked oil vapors from thecracking still through said upper chamber separately from the oilflowing through said lower chamber, means for subjecting the cracked oilvapors to reflux condensation within the upper chamber, means forfractionating the cracked oil vapors uncondensed in said upper chamber,and means providing a pressure balance connection between the chambersto release vapors from the lower cham- 1 ber into the upper chamber andto maintain the preheated .and cracked oil leaving said preheater andcracking still under substantially the same pressure, whereby thepressure at the inlet side of said pump is made to correspondsubstantially to the pressure of the oil leaving the cracking still.

8. In a petroleum refining system in which oil is passed undersubstantial pressure through a preheater and then through a crackingstill, a column comprising a vertically extending shell, a wall dividingthe interior of said shell into a lower chamber and an upper chamber andpreventing liquid from flowing from the upper chamber into the lowerchamber, means for passing preheated oil from said preheater throughsaid lower chamber, a pump for then discharging the preheated oil tosaid cracking still, said lower chamber having sufcient volume to permitthe preheated oil to surge therein, means for passing cracked oil vaporsfrom the cracking still through said upper chamber separately from theoil flowing through said lower chamber, means for subjecting the crackedoil vapors to reilux condensation within the upper chamber, means forpassing reflux condensate from said upper chamber to the cracking Zone,means for fractionating the cracked oil vapors uncondensed in Said upperchamber, and means providing .a pressure balance connection between thechambers to release vapors from the lower chamber into the upper chamberand to maintain the preheated and cracked oil leaving said preheater andcracking still under substantially the saine pressure, whereby thepressure at the inlet side of said pump is made to correspondsubstantially to the pressure of the oil leaving the cracking still.

9. In a petroleum refining system in which oil is passed undersubstantial pressure through a preheater and then through a crackingstill, a column comprising a vertically extending shell, a wall dividingthe interior of said shell into a lower chamber and an upper chamber andpreventing liquid from flowing from the upper chamber into the lowerchamber, means for passing preheated oil from said preheater throughsaid lower chamber, a pump for then discharging the preheated oil tosaid cracking still, said lower chamber having suicient volume to permitthe preheated oil to surge therein, means for passing cracked oil vaporsfrom the cracking still through said upper chamber sepfrom said upperchamber with the preheated oil flowing to the cracking still, means forfractionating the cracked oil vapors uncondensed in said upper chamber,and means providing a pressure balance connection between the chambersto release vapors from the lower chamber into the upper chamber and tomaintain the preheated and cracked oil leaving said preheater andcracking still under substantially the same pressure, whereby thepressure .at the inlet side li;

of said pump is made to correspond substantially to the pressure of theoil leaving the cracking still.

WILLIAM T. HANCOCK.

